Milo g



(NoModeL) M. G. KELLOGG. MULTIPLE SWITGHBOARD.

Patented Oct. .26, 1897.

NlTED STATES PATENT FFICE.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGG SlVITCHBOARD AND SUPPLY COMPANY, OF SAME PLACE.

M U LTlPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,331 1, dated October 26, 1897. Application filed November 29, 1889. Serial No. 332,013. (No model.)

To all whom it may concern:

Be it known that I, MILo G. KELLOGG, of Chicago,Illinois,temporarilyresidingatStuttgart,in the Empire of Germany,have invented certain new and useful Improvements in Multiple Switchboards for Telephone-Exchanges, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to a telephone-exchange system in which the subscribers lines are metallic-circuit lines connected to multiple switchboards; and it consists in a system of switching and of testing at any board to determine whether any line is in use. I place as many switchboards in the central office as are found necessary or desirable in order to properly answer the calls and connect and disconnect the subscribers lines. On each board I place for each line a springjack or other switch having two contactpieces which are insulated from each other, except by the circuit connections. Said switches are each adapted to receive a loopswitch plug, and when a plug is inserted to connect the two contact-pieces with the two contact-pieces of the plug, respectively, one of the contact-pieces of each switch should be so placed that a test-plug or similar device may be readily applied to it or so connected to a test-bolt that it can be readily connected with it. i

Figures 1 and 1 of the drawings are front views of sections of two multiple switchboards to which the same lines are connected. Fig. 2 is a diagram of the boards and their circuits and connections necessary to illustrate my invention. Fig. 3 shows an operators cord system adapted to be used with the switchboards. Fig. t is a diagram of the subscribers-station apparatus necessary to illustrate my invention. Fig. 5 shows an operators test outfit.

In the drawings like parts and apparatus are indicated by the same letters and figures of reference. 1

In Fig. 2, A is a sectional View of the switchboards shown in Fig. 1, and A is a sectional view of the switchboard shown in Fig. 1 the section being taken on the line (Z 6. Upon the rubber strips a b of the form substantially as shown are mounted the contacts g and j. These strips may be long enough to hold a convenient number of jacks.

H are square holes through the fronts of and at the edges of the strips, adapted to receive and guide the switch-plugs. The con tact-springs g g are mounted to the rear of and are parallel to the holes Z Z, to which they belong, as shown.

9' j are contact-pieces of the switches, so placed as to make the switch connections hereinafter described, and also to readily connect with a test-plug for purposes of testing. The switch-plugs are substantially as shown in Fig. 3.

The several parts are so made, shaped, and

adjusted that when a switch-plug is inserted into a switch the two contact-pieces of the plug form connection, respectively, with the two contact-pieces of the switch.

to and so in Fig. 2 are two line-annunciators at the central office for receiving signals from the subscribers stations.

Two lines are represented in Fig. 2, the two branches of one line being marked wire No. 1 and wire No. 1 respectively, and the two branches of the other line being marked wire No. 2 and wire No. 2 respectively.

The connections of the line-circuits may be traced from the test-contacts j in the jack at each board, line conductor No. 1 to the subscribers station, thence normally, or while the telephone is not switched for use, to the frame of the generator, normally-closed contacts p and q, short circuit 14, around the armature of said generator, circuit-breaking bell 2, conductor 15, switch-lever 7, contact 9, normally in electrical connection therewith, short circuit 13, around the receiver-circuit, line conductor No. 1 to central spring-contacts g at each board, the annunciator a; to ground at G. The connections of all the subscribers circuits are substantially the same.

While the subscribers telephone is off the switch-lever, and is thereby switchedfor use, the subscribers circuit is traced as follows: line conductor No. 1", short circuit '12 around the calling set, contact 10, now connected to lever 7 closes the transmitter-circuit containing the battery 6, the primary coil 4, transmitter 3, and the conductor 15'.

When the call-generator is operated, the usual automatic device well-known to telephone-engineers forces the spring-contact 17 away from the contact q, thereby opening the short circuit 14, and brings it into connection with the grounded contact 1" and normallyclosed contacts 16 and 17. Since the metallic circuit is open at centraL'the current will be thrown over the line conductor No. 1 and ground. When clearing out, the metallic circuit. is no longer open at central and the generator-current is thrown over this oi rcuit, th ereby operating the clearing-out annunciator. To prevent'the operation of the calling-annunciator while clearing out, the subscriber manually opens the contacts 16 and 17. Thus it will be seen the subscribers generator is between line conductor No. 1. and ground. While clearing out, the calling-generator is in the metallic circuit alone, between the two line conductors. While the generator is operated, the telephone mustbe'on its switch.

The existence of the short circuits 12, 13, and 14 around the telephone set, the calling set, and the generator switches those elements out'of' the line-circuit. .It is obvious thatthey' mightbe placed on open circuit instead. rious other obvious modifications might be used.

The signal-bell 2 is the ordinary vibrating bell or automatic circuit-breaker and has a resistance suitable to the circuit.

Each operator at the central station is provided with a test outfit like that shown in Fig. 5, comprising a test-battery B and test receiving instrument t, grounded onone side at G and on the other side .conne'oted to a test-plugp, adapted. to be applied to a testcontact j for testing.

The battery 13', the test receiving instrument t, and the subscribers vibrating bell 2 are so related that when in circuit with each receiving instrument 25 will no longer give an indication corresponding tothe automatic circuit-breaker 2, thus indicating that the line is busy. Thus the test depends entirely upon the condition of the subscribers outfit,

the test receiving instrument giving a continuous signal while the line is free, but giving a single tap when the line is busy.

When the line, tests free, the ringing bell at the s-ubscribers station may call the subscriber, informing him that he is Wanted at the telephone; but preferably this call is preliminary and short, and the call-generator B is used for the purpose of calling.

The system as constructed has another pcculiar advantage which will be described H later.

. tacts m and m.

In Fig. 3 are shown two connecting-plugs Dand D, each composed of insulating material n, upon which are mounted two con- The two contacts 4% are connected together by a flexible conductor 01. The two contacts m are connected together by a. flexible conductor d, in the circuit of which is-a looping-in switch Y, adapted to be placed upon pairs of contacts q q, r r, or

s s, and thereby loop into the circuit a clearing-out annunciator c, an operators tele- E other plug crossed by'the plate.

. that when one plug is inserted into the switch of a calling subscriber the operators outfit is on closed circuit through the contacts of the The weight usually used with the flexible conductors d d i insures a good electrical connection between i the contacts m m and the conducting-plate 0. ;When a plug is inserted into a switch, its 5 contacts make connection with the jack-contacts g andj The plugs may with some test systems be inserted either way, but preferi ably the plug-contacts on should be connected 5 to the jack-contacts g and the plug-contacts m connected to the jack-contacts j.

When two lines are connected together and the subscribers hang up their telephones and no clearing-out signal is sent in, the lines are said to be tied up.

If the telephones of both subscribers are 1 upon their levers and an operator at another 1 board tests either of the connected lines, the operators test outfit will be in circuit with the vibrating bells of both subscribers in parallel toacalling-line, with the result that the call- -ing-line forms a bridge across the two tiedand the line tested will indicate free. The testing operator then connects the tested line up lines, and when the operator loops her call-generator into this bridge for calling not only do the subscribers bells ring, but the clearing-out annunciator is operated at the board where the two lines are tied up, and the operator. thereat seeing the disconnectionsignal disconnects the tied-up lines. Thus when lines are left in this condition it is'dissolved when either line is wanted. Both con- 5 nected lines would test free and be connected I to and their tied-up connection be dissolved if they both were wanted at the same time.

The clearing-out annunciator of two con- 1 nected lines in use by both subscribers is not operated by the test-battery, because the testvcircuit established resolves itself into the well-known VVheatstone bridge, being traced from the ground through the test outfit to a test-contact, thence in multiple over the two I a clearing-out annunciator, thence from each scriber.

contact 9 through a call-annunciator, both air nunciators having an equal resistance, thence to ground. The clearing-out annunciator is thus in a iVheatstone bridge and is not operated by the test-battery B of the test outfit.

If one and only one of the subscribers telephones of two connected lines is upon its switch, this balance is destroyed, for a vibrating bell 2 contains a resistance much smaller than that of the subscribers telephone set, and the clearing-out annunciator will be operated by a testbattery, so that when two lines are tied up at a board because no clearing-out signal is sent, and one telephone is on and the other off its hook, a testing operator, although finding the line busy, will operate the clearing-out annunciator, so that the tied up condition is dissolved.

By constructing the subscribers call and telephone sets of equal resistance the clearing-out annunciator will not operate when either of two connected lines is tested and one telephone is on and the other telephone is off the hook. Thus this feature may be omitted whenever desired without altering the system in other respects.

The operation of the system is as follows: \Vhen a subscriber desires to call, he turns the crank of his generator and thereby temporarily connects his line with the ground, and, sending a calling-current over the line, operates his line-annunciator at the central office. He then removes his telephone from its switch, and the operator at the central office places one of a pair of plugs in the switch of the line where the call is indicated, and, placing the lever of the switch Y corresponding with the pair of plugs used on the contact-bolts connected with her telephoneloop, finds out what is wanted. She then places her test-plug on the contact-piece j of the switch of the line wanted as a test. If the test indicates that the line is not in use, the operator places the other plug of the pair used into the switch of the line, thus connecting them together. Then by moving the levers of the looping-in switch she loops a calling-battery into the circuit and calls the sub- Then she loops the clearing-out annunciator into the circuit. By moving the switch she may again loop in the calling-battery or loop in her telephone set to determine by listening whether two connected subscribers are through conversation.

The lineannunciators are polarized annunciators, constructed to be operated by only one polarity of current, and they and the operators test-batteries should be so connected into their respective circuits that the annunciators will not respond when a test is made to their lines.

The subscribers generators may give currents of alternate polarity (as they are more generally constructed) which will operate the line-annuciators, or they may be constructed so as to give currents of only one polarity, and in the latter case should be so connected into their respective lines as to operate their polarized line-annunciators.

It will be observed that in this system of switching and testing the office ground of a line is not removed where a line is switched with another line. This does not interfere with the working of the telephone system, as it is well known that one ground on a metallic telephone-circuit does not interfere with its operation.

It will also be observed that although the line-annunciators are not cut off from their lines when the lines are switched for conversation they are substantially switched from the metallic circuit by the conductor cl, containing the clearing-out annunciator, which acts as a shunt around the two annunciators, so that enough of the clearing-out current is shunted from the line-annunciators to prevent their operation. The circuit of a clearing-out current may be traced from one pole s of the subscribers generator, line conductor No. 1, to central, to contact g of the switch, where the line is connected, through the annunciator to the common ground connection, thence through the annunciator of the other connected line to the contact g of the jack, where the line is connected, these annunciators being short-circuited or shunted by the conductor d, containing the clearingout annunciator, connected to the two contact-springs g g of the two lines, thence over the line conductors Nos. 2 and 2 to contact jof the latter line, conductor d, contact j of the former line, line conductor No. 1 back to the other pole of the subscribers generator.

Although the ground has been shown as forming part of the call and test circuits, it is obvious that a metallic conductor might be substituted therefor. To effect this, a connection to a common wire would be substituted for each ground connection.

It is to be noted that at any time a subscriber while connected to another for conversation can call the attention of an operator by ringing his call-generator without opening contacts 16 and 17, thus operating the call-annunciator. The metallic circuit, containing two subscribers circuits, their resistances, and the clearing-out annunciator, is shunted by the call-circuit containing the call-annunciator. An operator can thus be signaled by the calling subscriber and can loop her apparatus into the connected circuit for calling or conversation, and either subscriber may when his circuit is thus tied up secure another connection, with the result that the tied-up condition will be dissolved.

Some features of the test system are used IIO only in exchanges where all of the line-circuits have approximately the same resistance.

same instead of three or more contact-pieces and leading-in wires for each switch, as in other metallic-circuit multiple-switchboard systems.

scriber manipulates the normally closed key in the ground connection of his generator to open the circuit and then operates the gen- There is then no circuit through the I line-annunciatorsand they will not be opererator.

ated, but the clearing-out annunciator in the circuit of the lines will be operated. The contacts 9 and the test instrument being permanently connected to ground are therefore permanently connected with eachother.

I claim as my invention and desire to secure by Letters Patent-- 1. In a multiple-switchboard exchange, av

test-circuit containing a circuit-interrupter at the subscribers station switched from so 3 as not to be a part of said circuit while the telephone is switched for use, but not otherwise, a polarized call-annunciator in said testcircuit so connected as not to be operated thereby, and a call-circuit associated with said annunciator.

2. In a multiple-switchboard exchange, a;

metallic test-circuit, comprisinga test signaling device at the s'ubscribers stat-ion auto-Q matically operated by the battery, a test re-i ceiving instrument adapted to respond thereto, a battery, a subscribers-telephone switch controlling said response, a call-circuit, a: conductor common to said call and test circuits, anda polarized call-annunciator in said conductor, so connected as not to respond to said test-battery.

3. In amultiple-switchboard exchange, mei tallic circuits, each comprising in the orderf named test contacts, one at eachboard, a line conductor, a test signaling device at the subi scribers station, a return-line conductor, a test receiving instrument and battery adapted to respond to said test signaling device,

and a test plug or device adapted to be connected toa test-contact for testing; in combination with a subscribers switch to prevent said response while the. telephone is switched for use but not otherwise.

4. In a multiple-switchboard exchange, a metallic circuit, closed at subscribers station.

normally open at central, one limbconnected the order named, test-contacts, one at each board, aline conductor, a normally closed subscribers circuit containing normally a circuitinterrupter at his station, said interrupter being switched therefrom while the telephone is switched for use, a return metallic line conductor, switch-contacts, one at each board, and a test outfit at each board including a test 5 receiving instrument and battery adapted to In sending clearing-out signals the subbe connected to a test-contact for testing.

6. In a multiple-switchboard exchange, in the order named, test-contacts, a metallic line conductor, a subscribers station outfit containing a test signaling device, a metallic return-line conductor, jack-contacts, a polarized annunciator, and a connection to a test plug or device containing a test-battery so connected as not to operate said annunciator, and a test receiving instrument adapted to respond to said test signaling device; in combination with a switch in said 'subscribers outfit preventing said response while the telephone is switched for use.

7. In a multiple-switchboard exchange, metallic circuits each comprising, in the order named, a test-contact at each of two or more boards, a line conductor, a subscribers outfit containing an interrupter normally in its circuit, but switched therefrom while the telephone is switched for use, and a generator grounded whileca'lling but not while clearing out, a return-line conductor, a polarized annunciator, and a ground connection; in combination with a grounded test outfit at each board adapted to be connected to a test contact and to respond to said interrupter, and double-cord connecting apparatus adapted to connect two of said metallic circuits together, with a clearing-out annunciator shunting the call-annunciators of said metallic circuits.

8. In a multiple-switchboard exchange, in

the order named, test-contacts, one at each board, a metallic line conductor, a subscribers circuit containing normally a circuit-interrupter at his station, said interrupter being switched therefrom while the telephone is switched for use, a return -line conductor, switch-contacts permanently connected thereto, one at each board, a polarized calLannunciator, anda connection to test outfits in multiple branches, one outfit at each board in cluding a test receiving instrument adapted to respond to said interrupter while testing and the subscribers telephone is not switched for use but not otherwise; in combination with a test-battery, in said test-circuit, so connected as not to operate said call-annunciator, and a-call-circuit and generator for operating said call-annunciator.

9. In a multiple-switchboard exchange, two telephone-circuits connected together for conversation through a clearing-out annuncia' tor, and a test-circuit associated therewith containing said annunciator in the bridge of a Wheatstone bridge.

10. In a' multiple-switchboard exchange, two metallic circuits the two limbs Of one connected to the two limbs of the other, one limb of each circuit being connected through a resistance to a test outfit and battery in a normally open bridge closed while testing, a clearing-out annunciator in a separate circuit connecting said limbs, and a circuit of substantially no resistance connecting the other limbs of said metallic circuits.

11. I11 a multiple-switchboard exchange, two circuits of substantially equal resistance connected together at a board into a combined circuit for conversation, a clearing-out annunciator in one side of said combined circuit, a normally open bridge closed for testing, containing a test-battery, connected at one end through call-annunciators of subup circuit, a bridge containing a test-battery, normally open at one end but closed for testing, connected at the other end through substantially equal resistances to both' sides of said clearing-out annunciator whereby on testing, said clearing-out annunciator will be operated and the tied-up condition dissolved.

18. In a multiple-switchboard exchange, two tied-up metallic circuits, a switch for each circuit at each board containing two contacts, one connected to each limb, connecting apparatus at each board to connect the two contacts of one circuit with the two contacts of another circuit, a clearing-out annunciator in said connecting apparatus, a testcircuit for said connected circuits, and a test outfit responding free while testing, said connected circuits, when their telephones are not switched for use, and an operators callgenerator adapted to be connected to said cir cuit to operate said clearing-out annunciator.

MILO G. KELLOGG.

WVitnesses:

FRANCES D. KELLOGG, MARGARETHA RIEHL. 

